The present invention relates to a special structure for the parcel carrier of a bicycle, which is lightweight while affording notable strength and rigidity. Conventional parcel carriers for bicycles include a variety of types, of which the most common are those mounted to the rear end of the bicycle.
Normally, the structure of such a parcel carrier will consist of a framework affording a horizontal uppermost shelf, positionable over the rear wheel of the bicycle, and on which objects to be transported can be placed and secured.
The framework is secured detachably to the bicycle by way of the forwardmost part of the shelf in a position beneath the backwardmost part of the saddle, utilizing a variety of familiar methods and means, and fastened, by way of appropriate fittings incorporated into the ends of at least two lateral members extending downward from the shelf, to corresponding anchor lugs afforded generally by the two rear angled struts of the bicycle frame near to the rear wheel axle slots.
There has been an increasingly discernible trend over time toward parcel carriers of this same type in which the overall weight is limited by fashioning the entire framework from metal rod, preferably of aluminum or another light alloy. Conventional structures embodied in this way normally afford limited rigidity and strength only, and indeed the forwardmost lateral members or arms, which operate under compressive stress, are unable by reason of their appreciable length to support combined compressive and bending loads of any consequence and cannot prevent the normal transverse stresses from eventually generating considerable and undesirable lateral oscillations and roll through the structure as a whole.
To obtain at least a limited increase in strength, the part of the framework constituting the shelf can be fitted with two or more lateral members and reinforced with transverse and/or longitudinal elements disposed in a variety of ways within the peripheral rectangular structure of the shelf proper.
This type of expedient neither prevents the transverse oscillations nor eliminates roll, however, or at least will do so only to a limited extent.
Attempts have been made to overcome such drawbacks, for example by adoption of a parcel carrier as disclosed in U.S. Pat. No. 4,154,382 (Blackburn). In this carrier, the rectangular element of the shelf is attached to no less than three members. The two forwardmost members each consist of a rod bent into a square U-shape and disposed with their respective transverse portions secured at intermediate positions on the shelf to the two longer sides of the rectangular frame. The third member consists of a rod bent into a V-shape of which the apex is directed upwards and secured centrally to the shorter rear side of the rectangular frame.
The shape of this third member, i.e. the V-shape, is designed essentially to incorporate components into the overall framework that will delimit tetrahedral structural elements which, by virtue of their geometry, should be non-deformable and thus prevent the aforementioned unwanted transverse oscillations.
In practice, the rear wheel has to revolve between the two divergent parts of the third member, which ideally would form a perfect Vee, and to revolve, moreover, at a point near to what should be the vertex of these two same parts. Accordingly, the vertex must have a discernible horizontal portion, so that the resulting structure does not form an exact triangle in relation to the anchorages but a quadrilateral, and is therefore still deformable to some degree.
The structure thus obtained is consequently more robust and rigid than traditional types but only to a limited extent.